Iodine has a high microbicidal activity and has an extremely low toxicity to human bodies, and therefore it is widely utilized as a component for microbicides.
As a solvent for such iodine microbicide composition, an aqueous solution is generally utilized, but iodine is hardly stable in an aqueous solution. Accordingly, when an iodine-containing aqueous solution is stored for a long period of time, iodine therein would decompose and the iodine concentration in the resulting solution would decrease.
This phenomenon is more remarkable when the iodine concentration in the solution is lower. Accordingly, in order to inhibit the decrease of the iodine content in a conventional iodine microbicide composition of an aqueous solution system, the iodine concentration in the aqueous solution should be made higher, being 0.5% or more, so as to maintain the stability of the aqueous solution.
However, it is known that the microbicidal activity of iodine becomes maximum when the concentration of the free active iodine (hereinafter referred to as "effective iodine concentration") is in the range of from 10 to 100 ppm, and therefore, if the iodine content is 0.5% or more, the concentration is too high to sufficiently display the microbicidal power. This is a problem. In fact, the effective iodine concentration of conventional iodine microbicide compositions is almost from about 6,000 to 17,000 ppm and, therefore, the microbicidal effect of such compositions is sacrificed for the stability of the iodine content therein.
In addition, if the iodine concentration is to high, there is another problem that the offensive odor is too strong and the substances to be protected from microbes by the microbicide would disadvantageously be colored.
Under these circumstances, it has been desired to develop an iodine microbicide composition having a low iodine concentration and having a high storage stability.
Japanese Patent Publication No. 2242/88 (corresponding to U.S. Pat. No. 4,271,149) illustrates an iodine microbicide composition with a low iodine concentration which, however, essentially uses an aqueous solution as a solvent, similar to the above-mentioned conventional microbicide, and, therefore, the microbicidal power of the composition could not be sufficient.
U.S. Pat. No. 4,151,275 teaches the use of a solvent containing an alcohol in a high concentration for an iodine composition having a high iodine concentration of from 1.8 to 2.2 g/100 ml. With this composition, however, none of the above-mentioned problems of the deterioration of the microbicidal activity because of the high iodine concentration, the unpleasant feeling because of the offensive odor and the coloration of the substances to be protected from microbes could be overcome.
In actual use, the conventional high iodine microbicidal compositions have various problems such that these must be diluted just before use and the dilution requires complicated operation and, therefore, construction articles, such as a stool, etc., could not be disinfected with ease.
Another means of spraying an iodine microbicide from an aerosol container containing the microbicide has been proposed. Such means is advantageous since these do not require dilution of the microbicide and the aerosol container can be used with ease. However, conventional aerosol containers contain metallic parts everywhere because of the gaseous pressure-resistance, and the metallic parts would be corroded by the metal-corroding action of the iodine microbicide in the container or the metallic parts would often have an influence on the stability of iodine in the microbicide to decrease the effective iodine concentration. Accordingly, it is unsuitable to put an iodine microbicide in an aerosol container with metallic parts.
It may be considered to form an aerosol container from a synthetic resin, but synthetic resins generally have a large iodine gas permeability. Therefore, if an iodine microbicide is filled in a synthetic resin container, the iodine would permeate through the container and diffuse out therefrom. Thus, it is also unsuitable to put an iodine microbicide in an aerosol container made of a synthetic resin.